The invention relates to a ball circulating unit for a linear ball guidance device. The device is movable along a guiding rail with a circular cross-section. The device at least partially encloses the guiding rail. The device includes several continuous loops of balls, which are distributed across the rail cross-section, and are guided in a cage. The cage includes a plurality of loops, each loop including a carrying portion, in which the balls project radially inwardly from the cage and rest against the guiding rail, a returning portion and deflecting portions which connect the carrying and returning portions at their ends. The carrying portion and returning portion extend parallel to the longitudinal axis. The cage is fixed in the circumferential and axial direction in the basic outer member. The cage generally is a multi-component cage including a plurality of inner segments which act as a guiding means for the carrying portions, returning portions and head pieces, which form the deflecting portions attached to their axial ends. The inner segments include axially extending guiding recesses of the carrying portions and, therebetween, guiding grooves which form one or two returning portions. Also, the head pieces and inner segments are centered relative to each other, in accordance with U.S. patent application Ser. No. 07/505,021, filed Apr. 4, 1990, entitled "Ball Circulation Unit for a Linear Ball Guide," now U.S. Pat. No. 5,051,001 the specification and drawings of which are hereby incorporated by reference.
It is an object of the present invention to provide a cage which is easy to produce and which enables more variation in number and arrangement of the carrying portions further optimizing the device.
In accordance with the invention, the objective is achieved by a cage which is divided into groups of inner segments. Each group includes at least a first and second inner segment, which are of different types, with at least one web arranged between the individual groups. The web has at least one guiding recess for the balls provided in carrying portions associated with the adjoining groups.
By dividing the cage into a number of inner segments and head pieces, it is possible to produce it by simple tooling. This is due to the fact that the joint is positioned in the region of the carrying portions. In consequence, the inner segments and head pieces may easily be produced from plastics by injection molding.
Furthermore, it is advantageous, as a result of arranging the inner segments in groups, to arrange two carrying portions each in the circumferential direction of the guiding rail, with the smallest possible distance therebetween, with the load in these directions being introduced into the guiding rail.
Furthermore, an objective is achieved by the inner segments and/or the webs centered at the head pieces. Thus, either at one end or at both ends of the device, the cage is provided with guiding recesses to guide the balls in the carrying portions. The advantage is that assembly is simplified since the cage with one head piece and all inner segments and webs can be inserted into the basic outer member in a pre-assembled condition.
For a cage partially enclosing a guiding rail, it is proposed to divide one web into two half-webs. Each half-web includes a guiding recess for the balls of each carrying portion adjacent the slot.
The webs preferably extend along the length of the basic outer member; they also secure to and extend above and below the head pieces.
The inner segments are held to the head pieces with axial centering journals engaging correspondingly formed through-bores in the head pieces. However, the inner segments may also be secured by a cap attached to the outer basic member.
From the following detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.